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Abstract:

A nitride semiconductor light-emitting device includes a nitride
semiconductor light-emitting element, a package substrate and an
optically transparent resin sealing portion. The nitride semiconductor
light-emitting element includes a substrate, a nitride semiconductor
multilayer portion having a light-emitting layer and a protective layer.
The nitride semiconductor multilayer portion is provided on the
substrate. The protective layer is provided on an upper portion of the
nitride semiconductor multilayer portion. The resin sealing portion seals
the nitride semiconductor light-emitting element that is mounted on the
package substrate. An air gap layer is formed in at least one of an area
between the substrate and the light-emitting layer in the nitride
semiconductor light-emitting element, an area between the light-emitting
layer and the protective layer in the nitride semiconductor
light-emitting element and an area in the package substrate.

Claims:

1. A nitride semiconductor light-emitting element comprising: a
substrate; a nitride semiconductor multilayer portion provided on the
substrate; and a protective layer provided on an upper portion of the
nitride semiconductor multilayer portion, wherein the nitride
semiconductor multilayer portion includes a light-emitting layer, and an
air gap layer is formed in at least one of an area between the substrate
and the light-emitting layer and an area between the light-emitting layer
and the protective layer.

2. The nitride semiconductor light-emitting element of claim 1, further
comprising: a current diffusion layer provided on the nitride
semiconductor multilayer portion, wherein the air gap layer is provided
between the current diffusion layer and the protective layer.

3. The nitride semiconductor light-emitting element of claim 1, wherein
the nitride semiconductor multilayer portion further includes: a first
nitride semiconductor layer provided between the substrate and the
light-emitting layer; and a second nitride semiconductor layer provided
between the light-emitting layer and the protective layer, and the air
gap layer is formed in at least one of an area within the first nitride
semiconductor layer and an area within the second nitride semiconductor
layer.

4. The nitride semiconductor light-emitting element of claim 1, further
comprising: a solid layer that is provided adjacent to the air gap layer
in a direction of a normal to a main surface of the light-emitting layer,
wherein the solid layer has a high refractive index contrast for the air
gap layer, and pairs with the air gap layer to form a reflective mirror.

5. The nitride semiconductor light-emitting element of claim 1, further
comprising: a joining electrode provided on an upper portion of the
nitride semiconductor multilayer portion; and a first highly reflective
electrode layer provided between the nitride semiconductor multilayer
portion and the joining electrode.

6. The nitride semiconductor light-emitting element of claim 1, wherein
the nitride semiconductor multilayer portion further includes a first
nitride semiconductor layer provided between the substrate and the
light-emitting layer, and the nitride semiconductor light-emitting
element further comprises: a contact electrode provided on an upper
portion of the first nitride semiconductor layer; and a second highly
reflective electrode layer provided between the first nitride
semiconductor layer and the contact electrode.

7. A nitride semiconductor light-emitting device comprising: a nitride
semiconductor light-emitting element including: a substrate; a nitride
semiconductor multilayer portion provided on the substrate and having a
light-emitting layer; and a protective layer provided on an upper portion
of the nitride semiconductor multilayer portion; a package substrate on
which the nitride semiconductor light-emitting element is mounted; and an
optically transparent resin sealing portion that seals the nitride
semiconductor light-emitting element mounted on the package substrate,
wherein an air gap layer is formed in at least one of an area between the
substrate and the light-emitting layer in the nitride semiconductor
light-emitting element, an area between the light-emitting layer and the
protective layer in the nitride semiconductor light-emitting element and
an area in the package substrate.

8. A method of manufacturing a nitride semiconductor light-emitting
element, the method comprising: a step of providing, on a substrate, a
nitride semiconductor multilayer portion having a light-emitting layer; a
step of providing a protective layer on an upper portion of the nitride
semiconductor multilayer portion; and a step of forming an air gap layer
in at least one of an area between the substrate and the light-emitting
layer and an area between the light-emitting layer and the protective
layer.

9. The method of manufacturing the nitride semiconductor light-emitting
element according to claim 8, the method further comprising: a step of
providing a solid layer that is adjacent to the air gap layer in a
direction of a normal to a main surface of the light-emitting layer, that
has a high refractive index contrast for the air gap layer and that pairs
with the air gap layer to form a reflective mirror.

Description:

[0001] This application is based on Japanese Patent Application No.
2011-181767 filed in Japan on Aug. 23, 2011, the contents of which are
hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a nitride semiconductor
light-emitting element, a nitride semiconductor light-emitting device and
a method of manufacturing a nitride semiconductor light-emitting element.

[0004] 2. Description of the Related Art

[0005] Conventionally, in a general nitride semiconductor light-emitting
element, on a sapphire substrate, an n-type nitride semiconductor layer,
a nitride semiconductor light-emitting layer, a p-type nitride
semiconductor layer and the like are sequentially provided. On each of
the side of the n-type nitride semiconductor layer and the side of the
p-type nitride semiconductor layer, an n-side electrode and a p-side
electrode for connection with an external power supply are formed. On the
substantially entire surface of the p-type nitride semiconductor layer,
in order to assist current diffusion within the p-type nitride
semiconductor layer, a transparent conductive film or the like formed
with, for example, ITO (indium tin oxide) is deposited as a current
diffusion layer.

[0006] Furthermore, on the upper portion of the current diffusion layer, a
reflective film is deposited. This reflective film is provided in order
to reflect light emitted from the nitride semiconductor light-emitting
layer to the current diffusion layer toward the sapphire substrate and
thereby enhance the efficiency of extracting light by the nitride
semiconductor light-emitting element. The reflective film is generally
formed with a metal material, such as Ag or Al, that has a high
reflectivity. For example, JP-A-2011-71444 and JP-A-2006-108161 propose a
nitride semiconductor light-emitting element in which a metal reflective
film is formed through an insulating film on a transparent conductive
film. Moreover, JP-A-2006-120913 proposes a nitride semiconductor
light-emitting element in which a metal reflective film is formed on a
transparent conductive film through a multiple reflective film formed
with a plurality of dielectric layers.

[0007] However, when the metal reflective film is formed in the nitride
semiconductor light-emitting element as in JP-A-2011-71444 and
JP-A-2006-108161, a phenomenon called migration occurs due to the effects
of as an electric field, an ambient humidity and the like acting on the
metal reflective film, and thus a reliability problem occurs. When the
multilayer reflective film is formed as in JP-A-2006-120913, since it is
necessary to deposit a few tens of reflective films so as to obtain a
high reflectivity, disadvantageously, it takes a long time, and it is
uneconomical in terms of cost.

SUMMARY OF THE INVENTION

[0008] The present invention is made to overcome the above problem; an
object of the present invention is to provide a nitride semiconductor
light-emitting element including a reflective mirror in which its cost is
low, its reflectivity is high and its reliability is high, a nitride
semiconductor light-emitting device and a method of manufacturing a
nitride semiconductor light-emitting element.

[0009] To achieve the above object, according to the present invention,
there is provided a nitride semiconductor light-emitting element
including: a substrate; a nitride semiconductor multilayer portion
provided on the substrate; and a protective layer provided on an upper
portion of the nitride semiconductor multilayer portion, in which the
nitride semiconductor multilayer portion includes a light-emitting layer,
and an air gap layer is formed in at least one of an area between the
substrate and the light-emitting layer and an area between the
light-emitting layer and the protective layer.

[0010] In the configuration described above, the reflective mirror
including the air gap layer is formed in at least one of the area between
the substrate and the light-emitting layer and the area between the
light-emitting layer and the protective layer. The reflective mirror has
a high reflectivity for the light emitted from the light-emitting layer.
The reflective mirror has no metal reflective film. This prevents the
reliability from being decreased due to the migration phenomenon. It is
therefore possible to obtain the nitride semiconductor light-emitting
element including the reflective mirror that has a low cost, a high
reflectivity and a high reliability.

[0011] Alternatively, in the nitride semiconductor light-emitting element
configured as described above, a current diffusion layer provided on the
nitride semiconductor multilayer portion is further included, and the air
gap layer is provided between the current diffusion layer and the
protective layer.

[0012] In the configuration described above, the reflective mirror that is
formed with "the current diffusion layer/the air gap layer/the protective
layer" and that has a three-layer structure is formed. The refractive
index contrast of the interface between the current diffusion layer and
the reflective mirror is high. Hence, the reflective mirror has a high
reflectivity for the light emitted from the light-emitting layer.

[0013] Alternatively, in the nitride semiconductor light-emitting element
configured as described above, the nitride semiconductor multilayer
portion further includes: a first nitride semiconductor layer provided
between the substrate and the light-emitting layer; and a second nitride
semiconductor layer provided between the light-emitting layer and the
protective layer, and the air gap layer is formed in at least one of an
area within the first nitride semiconductor layer and an area within the
second nitride semiconductor layer.

[0014] In the configuration described above, the reflective mirror
including the air gap layer is formed in at least one of the area within
the first nitride semiconductor layer and the area within the second
nitride semiconductor layer. Hence, the reflective mirror can be formed
in a position closer to the light-emitting layer. Thus, the light emitted
from the light-emitting layer can be more effectively reflected off the
reflective mirror. It is therefore possible to more enhance the
efficiency of utilizing the light emitted from the light-emitting layer.

[0015] Alternatively, in the nitride semiconductor light-emitting element
configured as described above, a solid layer that is provided adjacent to
the air gap layer in a direction of a normal to a main surface of the
light-emitting layer is further included, and the solid layer has a high
refractive index contrast for the air gap layer, and pairs with the air
gap layer to form a reflective mirror.

[0016] In the configuration described above, the solid layer that is
adjacent to the air gap layer in the direction of the normal to the main
surface of the light-emitting layer and that has a high refractive index
contrast for the air gap layer is provided. The solid layer pairs with
the air gap layer to form a DBR (distributed bragg reflector) mirror
functioning as the reflective mirror. Hence, in the interface between the
air gap layer and the solid layer, a high refractive index contrast is
obtained. It is therefore possible to further enhance the reflectivity of
the reflective mirror for the light emitted from the light-emitting
layer.

[0017] Alternatively, in the nitride semiconductor light-emitting element
configured as described above, a joining electrode provided on an upper
portion of the nitride semiconductor multilayer portion and a first
highly reflective electrode layer provided between the nitride
semiconductor multilayer portion and the joining electrode are further
included.

[0018] In the configuration described above, the first highly reflective
electrode layer is provided between the nitride semiconductor multilayer
portion and the joining electrode. Hence, the light emitted from the
light-emitting layer can be reflected off the first highly reflective
electrode layer. It is therefore possible to prevent the light emitted
from the light-emitting layer from being absorbed by the joining
electrode.

[0019] Alternatively, in the nitride semiconductor light-emitting element
configured as described above, the nitride semiconductor multilayer
portion further includes a first nitride semiconductor layer provided
between the substrate and the light-emitting layer, and the nitride
semiconductor light-emitting element further includes: a contact
electrode provided on an upper portion of the first nitride semiconductor
layer; and a second highly reflective electrode layer provided between
the first nitride semiconductor layer and the contact electrode.

[0020] In the configuration described above, the second highly reflective
electrode layer is provided between the first nitride semiconductor layer
and the contact electrode. Hence, the light emitted from the
light-emitting layer can be reflected off the second highly reflective
electrode layer. It is therefore possible to prevent the light emitted
from the light-emitting layer from being absorbed by the contact
electrode.

[0021] To achieve the above object, according to the present invention,
there is provided a nitride semiconductor light-emitting device
including: a nitride semiconductor light-emitting element including: a
substrate; a nitride semiconductor multilayer portion provided on the
substrate and having a light-emitting layer; and a protective layer
provided on an upper portion of the nitride semiconductor multilayer
portion; a package substrate on which the nitride semiconductor
light-emitting element is mounted; and an optically transparent resin
sealing portion that seals the nitride semiconductor light-emitting
element mounted on the package substrate, in which an air gap layer is
formed in at least one of an area between the substrate and the
light-emitting layer in the nitride semiconductor light-emitting element,
an area between the light-emitting layer and the protective layer in the
nitride semiconductor light-emitting element and an area in the package
substrate.

[0022] In the configuration described above, the reflective mirror
including the air gap layer is formed in at least one of the area between
the substrate and the light-emitting layer in the nitride semiconductor
light-emitting element, the area between the light-emitting layer and the
protective layer in the nitride semiconductor light-emitting element and
the area in the package substrate. The reflective mirror has a high
reflectivity for the light emitted from the light-emitting layer. The
reflective mirror has no metal reflective film. This prevents the
reliability from being decreased due to the migration phenomenon. It is
therefore possible to obtain the nitride semiconductor light-emitting
device including the reflective mirror that has a low cost, a high
reflectivity and a high reliability.

[0023] To achieve the above object, according to the present invention,
there is provided a method of manufacturing a nitride semiconductor
light-emitting element including: a step of providing, on a substrate, a
nitride semiconductor multilayer portion having a light-emitting layer; a
step of providing a protective layer on an upper portion of the nitride
semiconductor multilayer portion; and a step of forming an air gap layer
in at least one of an area between the substrate and the light-emitting
layer and an area between the light-emitting layer and the protective
layer.

[0024] In the configuration described above, the reflective mirror
including the air gap layer is formed in at least one of the area between
the substrate and the light-emitting layer and the area between the
light-emitting layer and the protective layer. The reflective mirror has
a high reflectivity for the light emitted from the light-emitting layer.
The reflective mirror has no metal reflective film. This prevents the
reliability from being decreased due to the migration phenomenon. It is
therefore possible to obtain the method of manufacturing the nitride
semiconductor light-emitting element including the reflective mirror that
has a low cost, a high reflectivity and a high reliability.

[0025] In the method of manufacturing the nitride semiconductor
light-emitting element configured as described above, a step of providing
a solid layer that is adjacent to the air gap layer in a direction of a
normal to a main surface of the light-emitting layer, that has a high
refractive index contrast for the air gap layer and that pairs with the
air gap layer to form a reflective mirror may be further included.

[0026] In the configuration described above, the solid layer that is
adjacent to the air gap layer in the direction of the normal to the main
surface of the light-emitting layer and that has a high refractive index
contrast for the air gap layer is provided. The solid layer pairs with
the air gap layer to form the DBR mirror functioning as the reflective
mirror. Hence, in the interface between the air gap layer and the solid
layer, a high refractive index contrast is obtained. It is therefore
possible to more enhance the reflectivity of the reflective mirror for
the light emitted from the light-emitting layer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to a first embodiment;

[0028] FIG. 2 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting element according to the first embodiment;

[0029] FIGS. 3A to 3F are cross-sectional views in the steps of
manufacturing the nitride semiconductor light-emitting element of the
first embodiment;

[0030] FIGS. 4A and 4B are graphs showing the characteristic of the
reflectivity of a reflective mirror according to the first embodiment;

[0031] FIG. 5 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to a second embodiment;

[0032] FIG. 6 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to a third embodiment;

[0033] FIG. 7 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to a fourth embodiment;

[0034] FIG. 8 is a diagram showing the structure of an example of a DBR
mirror that is formed by the pairing of an air gap layer with a solid
layer;

[0035] FIG. 9 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to a fifth embodiment;

[0036] FIG. 10 is a cross-sectional view showing the structure of a
nitride semiconductor light-emitting device according to a variation of
the fourth embodiment;

[0037] FIG. 11 is a cross-sectional view showing the structure of a
nitride semiconductor light-emitting device according to a sixth
embodiment; and

[0038] FIG. 12 is a cross-sectional view showing the structure of a
nitride semiconductor light-emitting device according to a seventh
embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Embodiments of the present invention will be described below with
reference to accompanying drawings. Although some embodiments of the
present invention are described below, specific configurations are not
limited to those of the embodiments. Even when design modifications and
the like are made without departing from the spirit of the present
invention, they are included in the present invention.

First Embodiment

[0040] FIG. 1 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to the first embodiment. As
shown in FIG. 1, the nitride semiconductor light-emitting device 1a of
the first embodiment includes a flip-chip nitride semiconductor
light-emitting element 10a, a package substrate 20 and a resin sealing
portion 30.

[0041] On one of the main surfaces of the package substrate 20, bumps 21A
and 21B are provided. On the other main surface, a p-side wiring pattern
22A and an n-side wiring pattern 22B are provided. In the package
substrate 20, through holes 23A and 23B that penetrate from one main
surface to the other main surface are provided. Within the through holes
23A and 23B, conductive paths are formed. The bump 21A is electrically
connected to the p-side wiring pattern 22A through the conductive path
formed within the through hole 23A. The bump 21B is electrically
connected to the n-side wiring pattern 22B through the conductive path
formed within the through hole 23B.

[0042] On the one main surface of the nitride semiconductor light-emitting
element 10a, a p-side joining electrode 14A and an n-side joining
electrode 14B are provided. When the nitride semiconductor light-emitting
element 10a is flip-chip mounted on the package substrate 20, the p-side
joining electrode 14A of the nitride semiconductor light-emitting element
10a is electrically connected to the bump 21A on the package substrate
20. Furthermore, the n-side joining electrode 14B of the nitride
semiconductor light-emitting element 10a is electrically connected to the
bump 21B on the package substrate 20.

[0043] The resin sealing portion 30 seals the flip-chip nitride
semiconductor light-emitting element 10a mounted on the one main surface
of the package substrate 20. The material of the resin sealing portion 30
is preferably an optically transparent material; it is not particularly
limited. The material of the resin sealing portion 30 may be a resin
material. Alternatively, the material of the resin sealing portion 30 may
be a composite resin material that contains a filling material having a
high thermal conductivity, a fluorescent member and the like.

[0044] The structure of the nitride semiconductor light-emitting element
10a according to the first embodiment will now be described in detail.
FIG. 2 is a cross-sectional view showing the structure of the nitride
semiconductor light-emitting element according to the first embodiment.
As shown in FIG. 2, the nitride semiconductor light-emitting element 10a
includes a substrate 11, a nitride semiconductor multilayer portion 12, a
current diffusion layer 13, the p-side joining electrode 14A (joining
electrode), the n-side joining electrode 14B, an n-side contact electrode
15 (contact electrode), a highly reflective electrode layers 16A to 16C,
a protective layer 17 and an air gap layer 191. The nitride semiconductor
multilayer portion 12 is composed of a plurality of nitride semiconductor
layers formed with a nitride semiconductor
(InxAlyGa1-x-yN: 0≦x<1, 0≦y<1). The
nitride semiconductor multilayer portion 12 includes a buffer layer 121,
an n-type contact semiconductor layer 122 (part of a first nitride
semiconductor layer), an n-type clad layer 123 (part of the first nitride
semiconductor layer), a light-emitting layer 124 and a p-type
semiconductor layer 125 (a second nitride semiconductor layer). The
nitride semiconductor light-emitting element 10a is substantially
rectangular when seen in the direction of a normal to its main surface.
However, the shape of the nitride semiconductor light-emitting element
10a is not limited to this shape.

[0045] The substrate 11 is, for example, a sapphire substrate. The
sapphire substrate has a main surface of (0001) plane direction. In the
main surface of the substrate 11, a plurality of convex portions 110 are
formed. The convex portion 110 is formed substantially in the shape of a
circular truncated cone or a circular cone. The height of the convex
portion 110 in the direction of the normal to the main surface of the
substrate 11 is, for example, 0.6 μm. In plan view seen in the
direction of the normal to the main surface of the substrate 11, the
planar shape of the convex portion 110 in the main surface of the
substrate 11 is, for example, a circle having a diameter of 1 μm. In
plan view seen in the direction of the normal to the main surface of the
substrate 11, the centers of the planar shapes of the individual convex
portions 110 in the main surface of the substrate 11 are positioned in
the individual apexes of imaginary regular triangles. The individual
convex portions 110 are regularly arranged so as to be aligned in the
directions of the three sides of the imaginary regular triangles. The
pitch between the individual convex portions 110 is, for example, 2
μm. As described above, a plurality of convex portions 110 are formed
in the main surface of the substrate 11, and thus it is possible to
enhance the inside quantum effect of the nitride semiconductor
light-emitting element 10a and the efficiency of extracting light.

[0046] Specifically, by a LEPS (lateral epitaxy on the patterned
substrate) method, the nitride semiconductor multilayer portion 12 having
a low dislocation density can be deposited on the main surface of the
substrate 11. In the LEPS method, for example, a crystal preferentially
grows substantially in the direction of the normal to the side surface of
the convex portion 110. Hence, in the process of the crystal growth, a
facet surface bends the dislocation inside a growing film. Consequently,
in the process of the crystal growth, the propagation of the dislocation
substantially in the direction of the normal to the main surface of the
substrate 11 is inhibited. Hence, the dislocation density inside the
growing film is reduced. It is therefore possible to enhance the inside
quantum effect of the nitride semiconductor light-emitting element 10a.

[0047] The refractive index of the nitride semiconductor multilayer
portion 12 is high. Hence, in general, light is more likely to be totally
reflected within the nitride semiconductor light-emitting element. On the
other hand, as in the nitride semiconductor light-emitting element 10a
according to the present embodiment, a plurality of convex portions 110
are formed in the main surface of the substrate 11, and thus it is
possible to reduce the scattering of light and the total reflection of
light. Moreover, the pitch between the individual convex portions 110 is
decreased, and thus it is possible to expect the diffraction effect of
light. It is therefore possible to enhance the efficiency of extracting
light by the nitride semiconductor light-emitting element 10a.

[0048] On the main surface of the substrate 11, the nitride semiconductor
multilayer portion 12 is deposited by the LEPS method. Specifically, the
n-type contact semiconductor layer 122 is deposited through the buffer
layer 121 formed with AlN. On a predetermined region on the upper surface
of the n-type contact semiconductor layer 122, the n-type clad layer 123
is deposited. In the following description, this region is referred to as
a first region. On the upper portion of the n-type clad layer 123, the
light-emitting layer 124 is deposited. The light-emitting layer 124 has a
multiple quantum well structure. In the multiple quantum well structure,
for example, a 3.5 nm thick n-type In0.15Ga0.85N quantum well
layer and, for example, a 6 nm thick Si-doped GaN barrier layer are
alternately deposited six times. On the light-emitting layer 124, the
p-type semiconductor layer 125 is deposited. The p-type semiconductor
layer 125 is formed of Mg-doped nitride semiconductor
(InxAlyGa1-x-yN: 0≦x<1, 0≦y<1). On the
p-type semiconductor layer 125, the current diffusion layer 13 is
deposited. The current diffusion layer 13 is formed of, for example, ITO
(indium tin oxide) having a thickness of 150 nm. On a region on the upper
surface of the current diffusion layer 13, the p-side joining electrode
14A is provided through the highly reflective electrode layer 16A.

[0049] On a region on the upper surface of the n-type contact
semiconductor layer 122 other than the first region, the n-side contact
electrode 15 is provided through the highly reflective electrode layer
16B. The upper surface of the n-side contact electrode 15 is
substantially as high as the upper surface of the current diffusion layer
13. Furthermore, on the n-side contact electrode 15, the n-side joining
electrode 14B is provided through a highly reflective electrode layer
16C.

[0050] The highly reflective electrode layers 16A to 16C are reflective
films that have a high reflectivity. The highly reflective electrode
layers 16A to 16C are provided so that light emitted from the
light-emitting layer 124 is not absorbed by the p-side joining electrode
14A, the n-side contact electrode 15 and the n-side joining electrode
14B. The highly reflective electrode layers 16A to 16C are formed of, for
example, Al, AG, Pt, Rh or the like; the present invention is not limited
to these substances. Preferably, the highly reflective electrode layers
16A to 16C have a high reflectivity for the light emitted from the
light-emitting layer and is formed of a conductive material.

[0051] On the regions where the highly reflective electrode layers 16B and
16C are formed and the upper surface of the nitride semiconductor
light-emitting element 10a other than the surfaces of the p-side joining
electrode 14A and the n-side joining electrode 14B (in other words, on
the main surface where the p-side joining electrode 14A and the n-side
joining electrode 14B are provided), the protective layer 17 is provided.
More specifically, the first region (the region where the n-type clad
layer 123 is provided), the upper surface of the n-type contact
semiconductor layer 122 other than the region where the highly reflective
electrode layer 16B is provided, the side surface of the nitride
semiconductor multilayer portion 12, the upper surface and the side
surface of the current diffusion layer 13 other than the region where the
highly reflective electrode layer 16A is provided and the upper surface
and the side surface of the n-side contact electrode 15 other than the
region where the highly reflective electrode layer 16C is provided are
covered with the protective layer 17.

[0052] On a region on the upper surface of the current diffusion layer 13
other than the region where the highly reflective electrode layer 16A is
provided, the air gap layer 191 is formed between the current diffusion
layer 13 and the protective layer 17. In the following description, this
region is referred to as a second region. The air gap layer 191 is an air
gap that is provided between the current diffusion layer 13 and the
protective layer 17. The thickness of the air gap layer 191 is
approximately an odd multiple of {λo×1/(4nair)}.
Here, λo/nair represents the wavelength of the light
emitted from the light-emitting layer 124 in air. Also, λo and
nair respectively represent the wavelength of the light emitted in
vacuum and the refractive index of the air gap layer 191 (in other words,
air). In fact, the refractive index of the air is approximately one.
Hence, the thickness of the air gap layer 191 is approximately an odd
multiple of {λo×1/4}, that is, approximately an odd
multiple of one-fourth of the wavelength of the light emitted from the
light-emitting layer 124 in vacuum.

[0053] The air gap layer 191 described above is formed, and thus a
reflective mirror 19 having a three-layer structure is formed on the
second region on the upper surface of the current diffusion layer 13. The
reflective mirror 19 is formed with "the current diffusion layer 13/the
air gap layer 191/the protective layer 17." In the reflective mirror 19
including the air gap layer 191 described above, the refractive index
contrast of the interface between the current diffusion layer 13 and the
air gap layer 191 is high. Hence, the reflective mirror 19 has a high
reflectivity for the light emitted from the light-emitting layer 124. The
reflective mirror 19 has no metal reflective film. This prevents the
reliability from being decreased due to the migration phenomenon.

[0054] In the steps of manufacturing the air gap layer 191, as described
later, a sacrifice layer 18 is formed on the second region on the upper
surface of the current diffusion layer 13. Furthermore, the protective
layer 17 is deposited. Thereafter, the sacrifice layer 18 is etched away.
Hence, in the upper portion of the second region, openings 171 are formed
in the protective layer 17. Although, in the present embodiment, the
openings 171 are provided on the upper portion of the air gap layer 191,
the openings 171 may be formed on the side of the air gap layer 191.
Preferably, at least one opening 171 is provided either on the upper
portion of or on the side of the air gap layer 191. The perimeter portion
of the opening 171 may be coated with, for example, a fluorine resin. In
this way, when the resin sealing portion 30 is formed, it is possible to
prevent the material of the resin sealing portion 30 from entering the
air gap layer 191 through the openings 171.

[0055] The method of manufacturing the nitride semiconductor
light-emitting element 10a of the first embodiment will now be described.
FIGS. 3A to 3F are cross-sectional views in the steps of manufacturing
the nitride semiconductor light-emitting element of the first embodiment.

[0056] The substrate 1 having the main surface of (0001) plane direction
is first prepared. A plurality of convex portions 110 are formed in the
main surface of the substrate 11 by photolithography and etching. Then,
as shown in FIG. 3A, on the main surface of the substrate 11 where the
convex portions 110 are formed, the nitride semiconductor multilayer
portion 12 is formed by the LEPS method.

[0057] Specifically, on the main surface of the substrate 11 where the
convex portions 110 are formed, the buffer layer 121 is formed.
Thereafter, the n-type contact semiconductor layer 122 and the n-type
clad layer 123 (the first nitride semiconductor layer) are sequentially
formed.

[0058] Under conditions in which the substrate temperature is about
890° C., on the n-type clad layer 123, the n-type
In0.15Ga0.85N quantum well layer is formed. Thereafter, the
Si-doped GaN barrier layer is formed. These steps are alternately
repeated six times. In this way, the light-emitting layer 124 having a
multiple quantum well structure is formed.

[0059] Then, on the light-emitting layer 124, the p-type semiconductor
layer 125 (the second nitride semiconductor layer) is formed. Thereafter,
as the current diffusion layer 13, an ITO transparent conductive film
having a thickness of 150 nm is formed on the p-type semiconductor layer
125 by sputtering. Here, the sheet resistance of the ITO transparent
conductive film formed as the current diffusion layer 13 is measured.
Consequently, the sheet resistance is about 200Ω.

[0060] After the formation of the current diffusion layer 13, under
conditions in which the substrate temperature is 600° C. in an
atmosphere of a mixture gas composed of 2% of oxygen and 98% of nitrogen,
first anneal processing is performed for 10 minutes. Thereafter, the
transmittance of the ITO transparent conductive film formed as the
current diffusion layer 13 is measured. Consequently, the transmittance
for light having a wavelength of 450 nm is increased to 94% or more.

[0061] After the completion of the first anneal processing, the current
diffusion layer 13 is temporarily exposed to the atmosphere. Thereafter,
the current diffusion layer 13 is returned again to a furnace, and, under
conditions in which the substrate temperature is 500° C. in
vacuum, second anneal processing is performed for 5 minutes. Then, the
sheet resistance of the ITO film formed as the current diffusion layer 13
is measured. Consequently, the sheet resistance is decreased to
11Ω. As described above, the second anneal processing is performed,
and thus it is possible to decrease the sheet resistance of the ITO
transparent conductive film formed as the current diffusion layer 13.

[0062] After the second anneal processing, a region on the upper surface
of the current diffusion layer 13 is partially etched by
photolithography. By first etching processing, as shown in FIG. 3B, the
current diffusion layer 13, the p-type semiconductor layer 125, the
light-emitting layer 124, the n-type clad layer 123 and the n-type
contact semiconductor layer 122 are partially removed. Here, in plan view
perpendicularly from above the upper surface of the current diffusion
layer 13, the regions other than the first region on the upper surface of
the n-type contact semiconductor layer 122 are exposed. The first region
is the region on which the n-type clad layer 123 is deposited.

[0063] On a region of the exposed region on the n-type contact
semiconductor layer 122, as shown in FIG. 3C, the n-side contact
electrode 15 is provided. Between the n-type contact semiconductor layer
122 and the n-side contact electrode 15, the highly reflective electrode
layer 16B is provided. These layers are formed, utilizing
photolithography, by electron-beam deposition and a lift-off method. For
example, photolithography is used to form a photoresist pattern on the
regions other than the region where the highly reflective electrode layer
16B is formed (that is, a region of the region where the n-type contact
semiconductor layer 122 is exposed) on the main surface of the nitride
semiconductor light-emitting element 10a in the state shown in FIG. 3B.
Then, the highly reflective electrode layer 16B and the n-side contact
electrode 15 are sequentially deposited by electron-beam deposition. The
n-side contact electrode 15 is deposited such that the upper surface of
the n-side contact electrode 15 is substantially as high as the upper
surface of the current diffusion layer 13. Thereafter, by the lift-off
method, the highly reflective electrode layer 16B and the n-side contact
electrode 15 formed on the photoresist pattern are removed together with
the photoresist pattern.

[0064] Then, as shown in FIG. 3D, the sacrifice layer 18 is formed on the
region (the second region) on the upper surface of the current diffusion
layer 13. The thickness of the sacrifice layer 18 is set at approximately
an odd multiple of {λo×1/(4nair)} Here,
λo/nair represents the wavelength of the light emitted
from the light-emitting layer 124 in air. Also, λo and
nair respectively represent the wavelength of the light emitted in
vacuum and the refractive index of the air. In fact, the refractive index
of the air is approximately one. Hence, the thickness of the sacrifice
layer 18 is set at approximately an odd multiple of
{λo×1/4}, that is, approximately an odd multiple of
one-fourth of the wavelength of the light emitted from the light-emitting
layer 124 in vacuum. Then, as shown in FIG. 3E, by plasma chemical vapor
deposition (PCVD), on the entire upper surface of the nitride
semiconductor light-emitting element 10a, the protective layer 17 is
formed. Examples of the material of the sacrifice layer 18 include Si, Al
and Cu; the present invention is not limited to these substances. The
material of the sacrifice layer 18 is preferably a material that
significantly differs in the etching characteristic from the protective
layer 17 and the current diffusion layer 13. As the material of the
protective layer 17, a photoresist material may be used as long as heat
is not applied in the process of forming the protective layer 17.

[0065] In the process of forming the protective layer 17, the openings 171
for removing the sacrifice layer 18 by etching on the upper portion of or
the side of the sacrifice layer 18 are provided in the protective layer
17. In the present embodiment, two openings 171 are formed. On the other
hand, the present invention is not limited to this. On the upper portion
of or the side of the sacrifice layer 18, at least one opening 171 is
preferably formed in the protective layer 17. After the formation of the
openings 171 in the protective layer 17, the perimeter portion of the
opening 171 may be coated with, for example, a fluorine resin. In this
way, when the resin sealing portion 30 is formed, it is possible to
prevent the material of the resin sealing portion 30 from entering the
air gap layer 191 through the openings 171.

[0066] After the formation of the protective layer 17, as shown in FIG.
3F, by photolithography, the sacrifice layer 18 is etched away. By this
etching processing, the air gap layer 191 is formed on the second region
on the upper surface of the current diffusion layer 13. Hence, the
thickness of the air gap layer 191 is approximately an odd multiple of
{λo×1/(4nair)}. In fact, the refractive index of
the air is approximately one. Hence, the thickness of the air gap layer
191 is approximately an odd multiple of {λo×1/4}. Thus,
on the second region on the upper surface of the current diffusion layer
13, the reflective mirror 19 having a three-layer structure is formed.
The reflective mirror 19 is formed with "the current diffusion layer
13/the air gap layer 191/the protective layer 17." In the reflective
mirror 19 including the air gap layer 191 described above, the refractive
index contrast of the interface between the current diffusion layer 13
and the air gap layer 191 is high. Hence, the reflective mirror 19 has a
high reflectivity for the light emitted from the light-emitting layer
124.

[0067] Then, by electron-beam deposition and photolithography, as shown in
FIG. 3F, on a region other than the second region on the upper surface of
the current diffusion layer 13, the protective layer 17 is removed.
Furthermore, the highly reflective electrode layer 16A and the p-side
joining electrode 14A are sequentially provided. Likewise, by
electron-beam deposition and photolithography, as shown in FIG. 3F, on a
region on the upper surface of the n-side contact electrode 15, the
protective layer 17 is removed. Furthermore, the highly reflective
electrode layer 16C and the n-side joining electrode 14B are sequentially
provided. Here, the p-side joining electrode 14A and the n-side joining
electrode 14B are provided such that the upper surface of the p-side
joining electrode 14A is substantially as high as the upper surface of
the n-side joining electrode 14B.

[0068] As described above, in the first embodiment, it is possible to
obtain the substantially rectangular flip-chip nitride semiconductor
light-emitting element 10a having the reflective mirror 19 that is formed
with "the current diffusion layer 13/the air gap layer 191/the protective
layer 17" and that has a three-layer structure.

[0069] The reflectivity characteristic of the reflective mirror 19
according to the first embodiment will now be described by comparison
with a comparative example where no air gap layer is formed. FIGS. 4A and
4B are graphs showing the characteristic of the reflectivity of the
reflective mirror according to the first embodiment. FIG. 4A is the graph
showing the result of a simulation of the reflectivity of the reflective
mirror with respect to light of wavelengths incident at an angle of
0°. FIG. 4B is the graph showing the result of a simulation of the
reflectivity of the reflective mirror with respect to light having a
wavelength of 450 nm incident at different angles. As shown in FIG. 4A,
the reflective mirror 19 of the first embodiment has a high reflectivity
of about 40% or more with respect to light in the wavelength range of 420
to 490 nm incident at an angle of 0°. By contrast, in the
comparative example where no air gap layer is formed, a low reflectivity
of 3% or less is only obtained. On the result of the measurement of the
reflectivity for the incident angle of light, likewise, with respect to
light having a wavelength of 450 nm incident at an angle of less than
20°, as shown in FIG. 4B, the reflective mirror 19 of the first
embodiment has a higher reflectivity than in the comparative example
where no air gap layer is formed.

[0070] As described above, in the nitride semiconductor light-emitting
device 1a of the first embodiment, the air gap layer 191 is provided
between the current diffusion layer 13 and the protective layer 17 in the
nitride semiconductor light-emitting element 10a. In this way, the
reflective mirror 19 that is formed with "the current diffusion layer
13/the air gap layer 191/the protective layer 17" and that has a
three-layer structure is formed. The refractive index contrast of the
interface between the current diffusion layer 13 and the air gap layer
191 is high. Hence, the reflective mirror 19 has a high reflectivity for
the light emitted from the light-emitting layer 124.

[0071] Although, in the first embodiment described above, the air gap
layer 191 is formed between the current diffusion layer 13 and the
protective layer 17, the present invention is not limited to this
configuration. Preferably, in the nitride semiconductor light-emitting
element 10a, the air gap layer 191 is formed in at least one of an area
between the substrate 11 and the light-emitting layer 124 and an area
between the light-emitting layer 124 and the protective layer 17. For
example, the air gap layer 191 may be formed either between the p-type
semiconductor layer 125 and the current diffusion layer 13 or within the
p-type semiconductor layer 125. Alternatively, the air gap layer 191 may
be provided either within the n-type contact semiconductor layer 122 or
within the n-type clad layer 123 or between the n-type contact
semiconductor layer 122 and the n-type clad layer 123.

[0072] In this way, it is possible to form the reflective mirror 19
including the air gap layer 191 in at least one of the area between the
substrate 11 and the light-emitting layer 124 and the area between the
light-emitting layer 124 and the protective layer 17. The reflective
mirror 19 has a high reflectivity for the light emitted from the
light-emitting layer 124. The reflective mirror 19 has no metal
reflective film. This prevents the reliability from being decreased due
to the migration phenomenon. It is therefore possible to obtain the
nitride semiconductor light-emitting element 10a including the reflective
mirror that has a low cost, a high reflectivity and a high reliability,
the nitride semiconductor light-emitting device 1a and the method of
manufacturing the nitride semiconductor light-emitting element 10a.

[0073] Although, in the first embodiment described above, one air gap
layer 191 is formed, a plurality of air gap layers 191 may be formed in
at least two areas or more among areas between the substrate 11 and the
light-emitting layer 124 and between the light-emitting layer 124 and the
protective layer 17. In this way, a plurality of reflective mirrors 19
including the air gap layer 191 are formed. It is therefore possible to
further enhance the efficiency of utilizing the light emitted from the
light-emitting layer 124.

Second Embodiment

[0074] A nitride semiconductor light-emitting device 1b of a second
embodiment will now be described. FIG. 5 is a cross-sectional view
showing the structure of the nitride semiconductor light-emitting device
according to the second embodiment. In the second embodiment, in addition
to the region on the upper surface of the current diffusion layer 13 of
the nitride semiconductor light-emitting device 1b, on the protective
layer 17, the highly reflective electrode layer 16A and the p-side
joining electrode 14A are sequentially provided. Except this point, the
second embodiment is the same as the first embodiment. The second
embodiment will be describe below; the same or corresponding portions as
or to those of the first embodiment are identified with like symbols.
Their description will not be repeated.

[0075] In the nitride semiconductor light-emitting device 1b of the second
embodiment, as shown in FIG. 5, in a nitride semiconductor light-emitting
element 10b, on the upper portion of the reflective mirror 19 that is
formed with "the current diffusion layer 13/the air gap layer 191/the
protective layer 17" and that has a three-layer structure, the highly
reflective electrode layer 16A is further provided. In this way, the
light emitted from the light-emitting layer 124 is reflected off not only
the reflective mirror 19 but also the highly reflective electrode layer
16A. It is therefore possible to further enhance the efficiency of
utilizing the light emitted from the light-emitting layer 124.

[0076] Although, in the second embodiment described above, the air gap
layer 191 is provided between the current diffusion layer 13 and the
protective layer 17, the present invention is not limited to this
configuration. Preferably, the air gap layer 191 is formed in at least
one of the area between the substrate 11 and the light-emitting layer 124
and the area between the light-emitting layer 124 and the protective
layer 17. A plurality of air gap layers 191 may be formed in at least two
areas or more among the areas between the substrate 11 and the
light-emitting layer 124 and between the light-emitting layer 124 and the
protective layer 17.

Third Embodiment

[0077] A nitride semiconductor light-emitting device 1c of a third
embodiment will now be described. FIG. 6 is a cross-sectional view
showing the structure of the nitride semiconductor light-emitting device
according to the third embodiment. In the third embodiment, a highly
reflective film 24 for reflecting the light emitted from the
light-emitting layer 124 is provided on the main surface of the package
substrate 20. Except this point, the third embodiment is the same as the
first embodiment. The same or corresponding portions as or to those of
the first embodiment are identified with like symbols. Their description
will not be repeated.

[0078] In the nitride semiconductor light-emitting device 1c, the highly
reflective film 24 is provided on the main surface of the package
substrate 20. Hence, the light emitted from the light-emitting layer 124
is also reflected off the highly reflective film 24 provided on the main
surface of the package substrate 20. It is therefore possible to further
enhance the efficiency of utilizing the light emitted from the
light-emitting layer 124. As the material of the highly reflective film
24, for example, Al, AG, Pt or Rh can be used; the present invention is
not limited to these substances. The material of the highly reflective
film 24 is preferably a material that has a high reflectivity for the
light emitted from the light-emitting layer 124.

[0079] As a variation of the third embodiment, the highly reflective film
24 described above may be provided on the main surface of the package
substrate 20 of the nitride semiconductor light-emitting device 1b
according to the second embodiment.

[0080] Although, in the third embodiment described above, the air gap
layer 191 is provided between the current diffusion layer 13 and the
protective layer 17, the present invention is not limited to this
configuration. Preferably, the air gap layer 191 is formed in at least
one of the area between the substrate 11 and the light-emitting layer 124
and the area between the light-emitting layer 124 and the protective
layer 17. A plurality of air gap layers 191 may be formed in at least two
areas or more among the areas between the substrate 11 and the
light-emitting layer 124 and between the light-emitting layer 124 and the
protective layer 17.

Fourth Embodiment

[0081] A nitride semiconductor light-emitting device 1d of a fourth
embodiment will now be described. FIG. 7 is a cross-sectional view
showing the structure of the nitride semiconductor device according to
the fourth embodiment. In the fourth embodiment, a nitride semiconductor
light-emitting element 10d further includes a solid layer 192. The solid
layer 192 is provided adjacent to the air gap layer 191 in the direction
of a normal to the main surface of the light-emitting layer 124 between
the current diffusion layer 13 and the protective layer 17. The solid
layer 192 is formed of a material that has a high refractive index
contrast for the air gap layer 191. The solid layer 192 pairs with the
air gap layer 191 to form a DBR (distributed bragg reflector) mirror 19A
functioning as the reflective mirror 19. The air gap layer 191 and the
solid layer 192 are alternately provided in the direction of the normal
to the main surface of the light-emitting layer 124. Except this point,
the fourth embodiment is the same as the first embodiment. The fourth
embodiment will be described below; the same or corresponding portions as
or to those of the first embodiment are identified with like symbols.
Their description will not be repeated.

[0082] FIG. 8 is a diagram showing the structure of an example of the DBR
mirror that is formed by the pairing of the air gap layer with the solid
layer. In FIG. 8, five air gap layers 191 and six solid layers 192 are
alternately provided in the following order: (solid layer 192)1/
(air gap layer 191)1/ (solid layer 192)2/ . . . / (solid layer
192)5/ (air gap layer 191)5/ (solid layer 192)6. They are
provided adjacent to each other in the direction of the normal to the
main surface of the light-emitting layer 124. Hence, on the second region
on the upper surface of the current diffusion layer 13, the DBR mirror
19A composed of five pairs of air gap layers 191 and solid layers 192 is
formed. In other words, on the second region on the upper surface of the
current diffusion layer 13, the DBR mirror 19A is formed that is formed
with "the current diffusion layer 13/the five pairs of (air gap layers
191 and solid layers 192)/the protective layer 17" and that has a
multi-layer structure. A part of sacrifice layer 18a, which will be
described later, is left in each of the air gap layers 191. Since the
part of sacrifice layer 18a supports the layers on and below the air gap
layer 191, the air gap layer 191 is unlikely to be broken.

[0083] The thickness of each air gap layer 191 of the DBR mirror 19A is
approximately an odd multiple of {λo×1/(4nair)}.
Here, λo/nair represents the wavelength of the light
emitted from the light-emitting layer 124 in air. Also, λo and
nair respectively represent the wavelength of the light emitted in
vacuum and the refractive index of the air gap layer 191 (that is, the
air). In fact, the refractive index of the air is approximately one;
hence, the thickness of the air gap layer 191 is approximately an odd
multiple of {λo×1/4}. The thickness of each solid layer
192 of the DBR mirror 19A is approximately an odd multiple of
{λo×1/(4nsc)}. Here, λo/nsc
represents the wavelength of the light emitted from the light-emitting
layer 124 in the solid layer 192. Also, λo and nsc
respectively represent the wavelength of the light emitted in vacuum and
the refractive index of the solid layer 192.

[0084] When, as in the fourth embodiment, the solid layer 192 is formed
between the current diffusion layer 13 and the protective layer 17,
sputtering, electron-beam deposition or the like is generally used.
Hence, in the fourth embodiment, the solid layer 192 is formed of a
dielectric material (especially, a dielectric material having excellent
optical characteristics) such as SiO2, SiN, TiO2 or like.

[0085] When, as described above, the solid layers 192 are provided such
that the solid layers 192 and the air gap layers 191 are alternately
adjacent to each other in the direction of the normal to the main surface
of the light-emitting layer 124, the air gap layers 191 pair with the
solid layers 192 to form the DBR mirror 19A functioning as the reflective
mirror 19. Hence, in the interface between the air gap layer 191 and the
solid layer 192, a high refractive index contrast is obtained. It is
therefore possible to further enhance the reflectivity of the DBR mirror
19A for the light emitted from the light-emitting layer 124. Furthermore,
in the DBR mirror 19A, as compared with a conventional DBR mirror, it is
possible to obtain a high reflectivity even when the number of layers (or
the number of pairs) is low.

[0086] The numbers and the alignment of air gap layers 191 and solid
layers 192 that constitute the DBR mirror 19A and the number of pairs of
air gap layers 191 and solid layers 192 are not limited to those of the
example of FIG. 8. Preferably, one or more of air gap layers 191 and one
or more of solid layers 192 are used. For example, m (an integer of one
or more) air gap layers 191 and (m-1) solid layers 192 may be provided
alternately and adjacently in the direction of the normal to the main
surface of the light-emitting layer 124 in the following order: (air gap
layer 191)1/ (solid layer 192)1/ (air gap layer 191)2/
(solid layer 192)2/ . . . / (solid layer 192)m-1/ (air gap
layer 191)m. Alternatively, for example, m air gap layers 191 and m
solid layers 192 may be provided alternately and adjacently on the
current diffusion layer 13 in the direction of the normal to the main
surface of the light-emitting layer 124 in the following order: (air gap
layer 191)1/ (solid layer 192)1/ (air gap layer 191)2/
(solid layer 192)2/ . . . / (air gap layer 191)m/ (solid layer
192)m.

[0087] In the nitride semiconductor light-emitting element 10d having the
DBR mirror 19A described above, in its manufacturing steps, a step of
forming the sacrifice layer 18 and a step of forming the reflective
mirror 19 are repeatedly performed on the second region on the upper
surface of the current diffusion layer 13. Thereafter, a step of removing
the sacrifice layer 18 by etching is performed.

[0088] For example, as in the first embodiment, the step of forming the
sacrifice layer 18 is performed on the second region on the current
diffusion layer 13. Thereafter, the solid layer 192 is formed on the
surface (for example, the upper surface and the side surface) of the
sacrifice layer 18, utilizing photolithography, by sputtering or
electron-beam deposition and the lift-off method. Here, on the upper
portion or the side of each sacrifice layer 18, openings (unillustrated)
for removing the sacrifice layers 18 by etching are provided in the solid
layer 192. As described above, a step of forming the sacrifice layer 18
on the formed solid layer 192 and a step of forming the solid layer 192
are repeatedly performed.

[0089] Then, desired numbers of sacrifice layers 18 and solid layers 192
are alternately formed in a desired order. Thereafter, an alternate
deposition structure of the sacrifice layers 18 and the solid layers 192
is patterned by the lift-off method and etching utilizing
photolithography. Then, the sacrifice layers 18 are removed by wet
etching, and thus the air gap layers 191 are formed. Here, an etching
solution having an etching rate selectivity for the sacrifice layer 18
and the solid layer 192 is used. Specifically, the etching solution in
which an etching rate for the sacrifice layer 18 is higher than that for
the solid layer 192 is used to form the air gap layer 191. When wet
etching is performed to remove the sacrifice layers 18, wet etching is
performed so as to leave the part 18a of the sacrifice layer 18. In this
way, within the air gap layer 191, the remaining part 18a of the
sacrifice layer 18 can support the layers on and below the air gap layer
191. It is therefore possible to prevent the air gap layer 191 from being
easily broken.

[0090] As described above, the desired numbers of air gap layers 191 and
solid layers 192 are alternately formed in the desired order, and thus
the air gap layers 191 pair with the solid layers 192 to form the DBR
mirror 19A functioning as the reflective mirror 19. Thereafter, plasma
chemical vapor deposition (PCVD) is performed to form the protective
layer 17 on the entire upper surface of the nitride semiconductor
light-emitting element 10d.

[0091] The thickness of each sacrifice layer 18 (in other words, the
thickness of each air gap layer 191) formed in the fourth embodiment is
set at approximately an odd multiple of
{λo×1/(4nair)}. In fact, the refractive index of
the air is approximately one. Hence, the thickness of each sacrifice
layer 18 is set at approximately an odd multiple of
{λo×1/4}. The thickness of each solid layer 192 is set
at approximately an odd multiple of {λo×1/(4nsc)}.
In the fourth embodiment, as the material of the sacrifice layer 18, a
dielectric material (especially, a dielectric material having excellent
optical characteristics) that has an etching characteristic significantly
different from that of the solid layer 192 is used.

[0092] In a variation of the fourth embodiment, as in the second
embodiment, in addition to the region on the upper surface of the current
diffusion layer 13, on the protective layer 17, the highly reflective
electrode layer 16A and the p-side joining electrode 14A may be
sequentially provided. Furthermore, in a variation of the fourth
embodiment, the same highly reflective film 24 as in the third embodiment
may be provided on the main surface of the package substrate 20. In this
way, the light emitted from the light-emitting layer 124 is reflected off
the highly reflective electrode layer 16A and the highly reflective film
24 provided on the main surface of the package substrate 20. It is
therefore possible to further enhance the efficiency of utilizing the
light emitted from the light-emitting layer 124.

[0093] Although, in the fourth embodiment described above, between the
current diffusion layer 13 and the protective layer 17, the DBR mirror
19A composed of the air gap layers 191 and the solid layers 192 is
formed, the DBR mirror 19A may be formed, for example, within the p-type
semiconductor layer 125.

Fifth Embodiment

[0094] FIG. 9 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to a fifth embodiment. In a
nitride semiconductor light-emitting element 10e of the nitride
semiconductor light-emitting device 1e according to the fifth embodiment,
for example, the DBR mirror 19A shown in FIG. 8 is provided within the
p-type semiconductor layer 125 instead of the second region on the upper
surface of the current diffusion layer 13. On the substantially entire
region of the upper surface of the current diffusion layer 13, the p-side
joining electrode 14A is provided through the highly reflective electrode
layer 16A. Except this point, the fifth embodiment is the same as the
first or fourth embodiment. The fifth embodiment will be describe below;
the same or corresponding portions as or to those of the first and fourth
embodiments are identified with like symbols. Their description may not
be repeated.

[0095] In the fifth embodiment, in the nitride semiconductor
light-emitting element 10e, the DBR mirror 19A can be formed in a
position closer to the light-emitting layer 124. Hence, the light emitted
from the light-emitting layer 124 can be more effectively reflected off
the DBR mirror 19A. It is therefore possible to more enhance the
efficiency of utilizing the light emitted from the light-emitting layer
124.

[0096] In the nitride semiconductor light-emitting element 10e described
above and having the DBR mirror 19A, while the p-type semiconductor layer
125 is being deposited so as to have a predetermined thickness, as in the
fourth embodiment, the step of forming the sacrifice layer 18 and the
step of forming the solid layer 192 are repeatedly performed. Thereafter,
the step of removing the sacrifice layer 18 is performed by etching. When
the solid layer 192 is formed within the nitride semiconductor layers of
the nitride semiconductor multilayer portion 12, a MOCVD method or the
like is generally used. Hence, in the fifth embodiment, the sacrifice
layer 18 and the solid layer 192 are formed of, for example, a
semiconductor material such as a nitride semiconductor
(InxAlyGa1-x-yN: 0≦x<1, 0≦y<1).

[0097] For example, as in the first and fourth embodiments, a p-type
semiconductor layer 125A is deposited to have a predetermined thickness.
Thereafter, the sacrifice layer 18 is formed on the upper surface of the
p-type semiconductor layer 125A. Then, the solid layer 192 is formed on
the surface (for example, the upper surface and the side surface) of the
sacrifice layer 18, utilizing photolithography, by sputtering or
electron-beam deposition and the lift-off method. Here, on the upper
portion or the side of each sacrifice layer 18, openings (unillustrated)
for removing the sacrifice layer 18 by etching are provided in the solid
layer 192. As described above, the step of forming the sacrifice layer 18
on the formed solid layer 192 and the step of forming the solid layer 192
are repeatedly performed.

[0098] Then, desired numbers of sacrifice layers 18 and solid layers 192
are alternately formed in a desired order. Thereafter, the sacrifice
layers 18 are removed by wet etching, and thus the air gap layers 191 are
formed. Here, an etching solution having an etching rate selectivity for
the sacrifice layer 18 and the solid layer 192 is used. Specifically, the
etching solution in which an etching rate for the sacrifice layer 18 is
higher than that for the solid layer 192 is used to form the air gap
layer 191. When wet etching is performed to remove the sacrifice layers
18, wet etching is performed so as to leave the part 18a of the sacrifice
layer 18. In this way, within the air gap layer 191, the remaining part
18a of the sacrifice layer 18 can support the layers on and below the air
gap layer 191. It is therefore possible to prevent the air gap layer 191
from being easily broken. Furthermore, the semiconductor material is used
to form the sacrifice layer 18 and the solid layer 192. Therefore, the
remaining part 18a of the sacrifice layer 18 is utilized, and thus it is
possible to achieve conductivity between the two solid layers 192 which
are formed on and below the air gap layer 191.

[0099] As described above, the desired numbers of air gap layers 191 and
solid layers 192 are alternately formed in the desired order, and thus
the air gap layers 191 pair with the solid layers 192 to form the DBR
mirror 19A functioning as the reflective mirror 19. In this way, the DBR
mirror 19A is formed, and then a p-type semiconductor layer 125B is
deposited again.

[0100] The thickness of each air gap layer 191 formed in the fifth
embodiment (in other words, the thickness of each sacrifice layer 18) is
set at approximately an odd multiple of
{λo×1/(4nair)}. Here, λo/nair
represents the wavelength of the light emitted from the light-emitting
layer 124 in air. Also, λo and nair respectively
represent the wavelength of the light emitted in vacuum and the
refractive index of the air gap layer 191 (that is, the air). In fact,
the refractive index of the air is approximately one. Hence, the
thickness of each sacrifice layer 18 is set at approximately an odd
multiple of {λo×1/4}. The thickness of each solid layer
192 is set at approximately an odd multiple of
{λo×1/(4nsc)}. Here, λo/nsc
represents the wavelength of the light emitted from the light-emitting
layer 124 in the solid layer 192. Also, λo and nsc
respectively represent the wavelength of the light emitted in vacuum and
the refractive index of the solid layer 192. In the fifth embodiment, as
the material of the sacrifice layer 18, a semiconductor material that has
an etching characteristic significantly different from that of the solid
layer 192 is used. As the material of the solid layer 192, a
semiconductor material that has a high refractive index contrast for the
air gap layer 191 is used.

[0101] In the fifth embodiment, the DBR mirror 19A is formed within the
p-type semiconductor layer 125. On the other hand, the present invention
is not limited to this configuration. The DBR mirror 19A is preferably
formed between the light-emitting layer 124 and the protective layer 17.
FIG. 10 is a cross-sectional view showing the structure of a nitride
semiconductor light-emitting device according to a variation of the fifth
embodiment. In a nitride semiconductor light-emitting element 10f of the
nitride semiconductor light-emitting device 1f according to the variation
of the fifth embodiment shown in FIG. 10, for example, the DBR mirror 19A
shown in FIG. 8 is provided between the p-type semiconductor layer 125
and the current diffusion layer 13 instead of the second region on the
upper surface of the current diffusion layer 13. In this way, the DBR
mirror 19A can also be formed in a position close to the light-emitting
layer 124. Hence, the light emitted from the light-emitting layer 124 can
be more effectively reflected off the DBR mirror 19A. It is therefore
possible to more enhance the efficiency of utilizing the light emitted
from the light-emitting layer 124.

[0102] In another variation of the fifth embodiment, as in the second
embodiment, in addition to the region on the upper surface of the current
diffusion layer 13, on the protective layer 17, the highly reflective
electrode layer 16A and the p-side joining electrode 14A may be
sequentially provided. Furthermore, in another variation of the fifth
embodiment, the same highly reflective film 24 as in the second
embodiment may be provided on the main surface of the package substrate
20. In this way, the light emitted from the light-emitting layer 124 is
also reflected off the highly reflective electrode layer 16A and the
highly reflective film 24 provided on the main surface of the package
substrate 20. It is therefore possible to further enhance the efficiency
of utilizing the light emitted from the light-emitting layer 124.

[0103] Although, as described above, in the first to fifth embodiments
described above, in the nitride semiconductor light-emitting element 10,
the reflective mirror 19 is provided between the light-emitting layer 124
and the protective layer 17, when the nitride semiconductor
light-emitting element 10 is not fillip-chip mounted on the package
substrate 20, the reflective mirror 19 may be provided between the
substrate 11 and the light-emitting layer 124.

Sixth Embodiment

[0104] FIG. 11 is a cross-sectional view showing the structure of a
nitride semiconductor light-emitting element according to a sixth
embodiment. As shown in FIG. 11, in the nitride semiconductor
light-emitting element 10g of the sixth embodiment, for example, the DBR
mirror 19A shown in. FIG. 8 is formed within the n-type contact
semiconductor layer 122. On the upper surface of the current diffusion
layer 13, the protective layer 17 is formed on the region (the second
region) other than the region where the highly reflective electrode layer
16A is provided. The configuration of the nitride semiconductor
light-emitting element 10g other than what has been described above is
the same as that of the nitride semiconductor light-emitting element 10a
according to the first embodiment.

[0105] In a nitride semiconductor light-emitting device (unillustrated) of
the sixth embodiment, the nitride semiconductor light-emitting element
10g is not flip-chip mounted. The nitride semiconductor light-emitting
element 10g is mounted on the package substrate 20 using, for example,
wiring. Furthermore, the nitride semiconductor light-emitting element 10g
is mounted on the package substrate 20 such that, in the direction of the
normal to the main surface of the package substrate 20, the DBR mirror
19A of the nitride semiconductor light-emitting element 10g is arranged
closer to the side of the package substrate 20 than to the light-emitting
layer 124. For example, the nitride semiconductor light-emitting element
10g is mounted on the package substrate 20 such that the main surface of
the nitride semiconductor light-emitting element 10g on the side of the
substrate 11 is opposite the main surface of the package substrate 20.

[0106] In the sixth embodiment, the same or corresponding portions as or
to those of the first embodiment are identified with like symbols. Their
description may not be repeated.

[0107] In the sixth embodiment, in the nitride semiconductor
light-emitting element 10g, the DBR mirror 19A can be formed in a
position closer to the light-emitting layer 124. Hence, the light emitted
from the light-emitting layer 124 can be more effectively reflected off
the DBR mirror 19A. It is therefore possible to more enhance the
efficiency of utilizing the light emitted from the light-emitting layer
124.

[0108] In the nitride semiconductor light-emitting element 10g described
above and having the DBR mirror 19A, while the n-type contact
semiconductor layer 122 is being deposited so as to have a predetermined
thickness, as in the fifth embodiment, the step of forming the sacrifice
layer 18 and the step of forming the solid layer 192 are repeatedly
performed. Thereafter, the step of removing the sacrifice layer 18 by
etching is performed. When the solid layer 192 is formed within the
nitride semiconductor layers of the nitride semiconductor multilayer
portion 12, the MOCVD method or the like is generally used. Hence, in the
sixth embodiment, the sacrifice layer 18 and the solid layer 192 are
formed of, for example, a semiconductor material such as a nitride
semiconductor (InxAlyGa1-x-yN: 0≦x<1,
0≦y<1).

[0109] For example, in a step of depositing the nitride semiconductor
multilayer portion 12, an n-type contact semiconductor layer 122A is
deposited to have a predetermined thickness. Thereafter, the sacrifice
layer 18 is formed on the upper surface of the n-type contact
semiconductor layer 122A. Then, the solid layer 192 is formed on the
surface (for example, the upper surface and the side surface) of the
formed sacrifice layer 18, utilizing photolithography, by sputtering or
electron-beam deposition and the lift-off method. Here, on the upper
portion or the side of each sacrifice layer 18, openings (unillustrated)
for removing the sacrifice layer 18 by etching are provided in the solid
layer 192. As described above, the step of forming the sacrifice layer 18
on the formed solid layer 192 and the step of forming the solid layer 192
are repeatedly performed.

[0110] Then, desired numbers of sacrifice layers 18 and solid layers 192
are alternately formed in a desired order. Thereafter, the sacrifice
layers 18 are removed by wet etching, and thus the air gap layers 191 are
formed. Here, an etching solution having an etching rate selectivity for
the sacrifice layer 18 and the solid layer 192 is used. Specifically, the
etching solution in which an etching rate for the sacrifice layer 18 is
higher than that for the solid layer 192 is used to form the air gap
layer 191. When wet etching is performed to remove the sacrifice layers
18, the wet etching is performed so as to leave the part 18a of the
sacrifice layer 18. In this way, within the air gap layer 191, the
remaining part 18a of the sacrifice layer 18 can support the layers on
and below the air gap layer 191. It is therefore possible to prevent the
air gap layer 191 from being easily broken. Furthermore, the
semiconductor material is used to form the sacrifice layer 18 and the
solid layer 192. Therefore, the remaining part 18a of the sacrifice layer
18 is utilized, and thus it is possible to achieve conductivity between
the two solid layers 192 formed on and below the air gap layer 191.

[0111] As described above, the desired numbers of air gap layers 191 and
solid layers 192 are alternately formed in the desired order. Thus, the
air gap layers 191 pair with the solid layers 192 to form the DBR mirror
19A functioning as the reflective mirror 19. In this way, the DBR mirror
19A is formed, and then an n-type contact semiconductor layer 122B is
deposited again.

[0112] The thickness of each air gap layer 191 formed in the sixth
embodiment (in other words, the thickness of each sacrifice layer 18) is
set at approximately an odd multiple of
{λo×1/(4nair)}. In fact, the refractive index of
the air is approximately one. Hence, the thickness of each sacrifice
layer 18 is set at approximately an odd multiple of
{λo×1/4}. The thickness of each solid layer 192 is set
at approximately an odd multiple of {λo×1/(4nsc)}.
In the sixth embodiment, as the material of the sacrifice layer 18, a
semiconductor material that has an etching characteristic significantly
different from that of the solid layer 192 is used. As the material of
the solid layer 192, a semiconductor material that has a high refractive
index contrast for the air gap layer 191 is used. If it is possible to
acquire a conductive path between the current diffusion layer 13 and the
n-side joining electrode 14B, as the materials of the sacrifice layer 18
and the solid layer 192, a dielectric material (especially, a dielectric
material having excellent optical characteristics) such as SiO2,
SiN, TiO2 or like may be used.

[0113] In the sixth embodiment, in the nitride semiconductor
light-emitting element 10g, the DBR mirror 19A is formed within the
n-type contact semiconductor layer 122. On the other hand, the present
invention is not limited to this configuration. The DBR mirror 19A is
preferably formed between the substrate 11 and the light-emitting layer
124. For example, in a variation of the sixth embodiment, the DBR mirror
19A may be formed between the n-type contact semiconductor layer 122 and
the n-type clad layer 123. In this way, the DBR mirror 19A can also be
formed in a position close to the light-emitting layer 124. Hence, the
light emitted from the light-emitting layer 124 can be more effectively
reflected off the DBR mirror 19A. It is therefore possible to more
enhance the efficiency of utilizing the light emitted from the
light-emitting layer 124.

[0114] In another variation of the sixth embodiment, the same highly
reflective film 24 as in the third embodiment may be provided on the main
surface of the package substrate 20. In this way, the light emitted from
the light-emitting layer 124 is also reflected off the highly reflective
film 24 provided on the main surface of the package substrate 20. It is
therefore possible to further enhance the efficiency of utilizing the
light emitted from the light-emitting layer 124.

[0115] Although, as described above, in the nitride semiconductor
light-emitting device 1 according to the first to sixth embodiments
described above, the reflective mirror 19 is provided in the nitride
semiconductor light-emitting element 10, the reflective mirror 19 may be
provided in the package substrate 20.

Seventh Embodiment

[0116] FIG. 12 is a cross-sectional view showing the structure of a
nitride semiconductor light-emitting device according to a seventh
embodiment. In the nitride semiconductor light-emitting device 1h of the
seventh embodiment, instead of between the light-emitting layer 124 and
the protective layer 17 in a nitride semiconductor light-emitting element
10h and between the substrate 11 and the light-emitting layer 124, for
example, the DBR mirror 19A shown in FIG. 8 is provided within the
package substrate 20. Except this point, the seventh embodiment is the
same as the first to sixth embodiments. In the seventh embodiment, the
same or corresponding portions as or to those of the first to sixth
embodiments are identified with like symbols. Their description will not
be repeated.

[0117] In the nitride semiconductor light-emitting device 1h, for example,
the DBR mirror 19A is provided within the package substrate 20. Hence,
the light emitted from the light-emitting layer 124 is reflected off the
DBR mirror 19A that is provided in the package substrate 20 and that has
a high reflectivity. It is therefore possible to more effectively utilize
the light emitted from the light-emitting layer 124.

[0118] In the seventh embodiment, the DBR mirror 19A is formed within the
package substrate 20. On the other hand, the present invention is not
limited to this configuration. For example, the DBR mirror 19A may be
provided on the upper surface (the main surface on the side where the
bumps 21A and 21B are provided) of the package substrate 20.
Alternatively, the DBR mirror 19A may be provided on the back surface
(the main surface on the side where the p-side wiring pattern 22A and the
n-side wiring pattern 22B are provided) of the package substrate 20.

[0119] In a variation of the seventh embodiment, in the nitride
semiconductor light-emitting device 1h, as in the second embodiment, in
addition to the region on the upper surface of the current diffusion
layer 13, on the protective layer 17, the highly reflective electrode
layer 16A and the p-side joining electrode 14A may be sequentially
provided. Moreover, in a variation of the seventh embodiment, in the
nitride semiconductor light-emitting device 1h, the same highly
reflective film 24 as in the third embodiment may be further provided on
the main surface of the package substrate 20. In this way, the light
emitted from the light-emitting layer 124 is reflected off the highly
reflective electrode layer 16A of the nitride semiconductor
light-emitting device 1h and the highly reflective film 24 provided on
the main surface of the package substrate 20. It is therefore possible to
further enhance the efficiency of utilizing the light emitted from the
light-emitting layer 124.

[0120] As described above, in the nitride semiconductor light-emitting
device 1 according to the first to seventh embodiments, the reflective
mirror 19 is provided in at least one of an area between the
light-emitting layer 124 and the protective layer 17 in the nitride
semiconductor light-emitting element 10, an area between the substrate 11
and the light-emitting layer 124 and an area in the package substrate. On
the other hand, the present invention is not limited to this
configuration.

[0121] The reflective mirror 19 is preferably provided in at least one of
the area between the light-emitting layer 124 and the protective layer 17
in the nitride semiconductor light-emitting element 10, the area between
the substrate 11 and the light-emitting layer 124 and the area in the
package substrate. For example, in the nitride semiconductor
light-emitting element 10, the reflective mirror 19 may be provided both
between the light-emitting layer 124 and the protective layer 17 and
between the substrate 11 and the light-emitting layer 124. In this way,
in the nitride semiconductor light-emitting element 10, the light emitted
from the light-emitting layer 124 can be reflected off the reflective
mirror 19 formed between the light-emitting layer 124 and the protective
layer 17 and the reflective mirror 19 formed between the substrate 11 and
the light-emitting layer 124. It is therefore possible to further enhance
the efficiency of utilizing the light emitted from the light-emitting
layer 124.

[0122] For example, the reflective mirror 19 may be provided, as in the
first to sixth embodiments, on the nitride semiconductor light-emitting
element 10 and may also be provided, as in the seventh embodiment, in the
package substrate 20. In this way, the light emitted from the
light-emitting layer 124 can be reflected off the reflective mirror 19
provided between the light-emitting layer 124 and the protective layer 17
and the reflective mirror 19 provided between the substrate 11 and the
light-emitting layer 124. It is therefore possible to further enhance the
efficiency of utilizing the light emitted from the light-emitting layer
124.

[0123] In the nitride semiconductor light-emitting device 1 according to
the first to seventh embodiments, in the nitride semiconductor
light-emitting element 10, the n-type contact semiconductor layer 122 and
the n-type clad layer 123 are provided, as the first nitride
semiconductor layer, between the substrate 11 and the light-emitting
layer 124. Furthermore, the p-type semiconductor layer 125 is provided,
as the second nitride semiconductor layer, on the light-emitting layer
124. On the other hand, the present invention is not limited to this
configuration. In the first to seventh embodiments, in the nitride
semiconductor light-emitting element 10, a p-type contact semiconductor
layer and a p-type clad layer may be provided, as the first nitride
semiconductor layer, between the substrate 11 and the light-emitting
layer 124. Furthermore, the n-type semiconductor layer may be provided,
as the second nitride semiconductor layer, on the light-emitting layer
124.

[0124] The description has been given based on the embodiments of the
present invention. The embodiments are illustrative; those skilled in the
art understand that many variations of the combinations of the components
and the types of processing are possible, and that they are within the
scope of the present invention.

[0125] The present invention can be utilized for nitride semiconductor
laser elements, light-emitting elements such as a LED, light-emitting
devices on which light-emitting elements are mounted and the like.